Global Navigation Satellite Systems (GNSS) allow navigation services including automatic route calculation from a current location to a destination location and guiding a driver of a vehicle to that destination with real time instructions in conjunction with a visual display of route segments as the vehicle progresses along the route.
The satellites transmit GPS signals comprising very precise location parameters and timing signals that are received by wireless device processors allowing a processor to determine their respective three dimensional positions and velocities.
A common car navigation system operates by computing an optimal route from the starting position to the desired destination point. The entire route is computed at once at the beginning of the routing and then the user is guided along the precomputed route.
Often, the user diverges from the original precomputed route, the result of an error to follow the guidance or as a user desired detour or by design. Such deviation is automatically detected by the auto routing system and in most cases a new route is computed. This is called auto-rerouting and in a majority of the cases a new route is computed following the same rule and the same algorithm as was used in the original route with the only difference that the new start point is the actual vehicle location at the time when the car navigation system determined that the user is off the original course.
Considering the processing time required to reroute from the current position to the destination after detection of a deviation from route, it is possible that a new route is determined only after the vehicle has passed the intersection. If this should happen, the driver will have passed the intersection without knowing the direction which should have been taken at the intersection in accordance with the search results. Therefore, the driver may well go in a direction different from the direction indicated by the search results and be further from the intended destination.